1. Field of the Invention
This invention relates generally to reticulated foam carriers in combination with two or more corrosion inhibitors impregnated therein that synergistically coact to provide quicker and longer corrosion protection in environments hostile to even the carrier. More specifically, to a high density carrier for holding either separate or in combination one, two, three or more volatile corrosion inhibitors of different vapor pressures. The carrier's rugged, relatively inert, highly flexible, open reticulated nature, and appropriately high chemical resistance, permits and enables the carrier, with vapor phase inhibitor systems, to be placed in remote, corrosive and environmentally hostile locations.
The present invention comprised an improvement to the corrosion inhibiting art: (a) through the use of foams such as isocyanate-derived polymer foams, or reticulated isocyanate-derived polymer foams, that possess both high chemical and physical resistance to hostile environments and also possess a large available volume capable of holding (b) one, two, three or more corrosion inhibitors of different vapor pressures.
The concept of foams and reticulated foams are known in the art. Reticulated foams are described in U.S. Pat. No. 3,025,200. The reticulated foams are noted for their improved compression/deflection characteristics including increased tear and tensile strength, elongation and surface-volume ratios. One feature of the present invention is the discovery that one can use isocyanate-derived polymer foams or partially reticulated isocyanate-derived polymer foams to provide, (a) a surprisingly high environmentally wet or dry stability and resistance that is far greater than foam rubber or the known cellulosic materials and (b) a more efficient and more effective carrier for volatile corrosion inhibitors than the known foam rubber or cellulosic materials such as Kraft Paper, cloth, paper-board or felt.
It was further discovered in this invention, that the protection provided by this foam and the greater working surface area provided to the corrosion inhibitor by impregnation, retention, distribution and deposition in the boundless multiple of cavities of the reticulated foam resulted in a more rapidly attained and longer sustained effective levels in the vapor pressure curve and the area under the curve was greatly enhanced. Furthermore, the area between the curve and the critical effective level line (both lines were virtually parallel) was elongated and essentially rectangular. This is in sharp contrast to the normally experienced slow but continued reduction of the corrosion inhibitor's efficiency levels and their continually dwindling partial pressures with time and concurrent with the progressive contraction of the total surface area during the volatilization era. This invention overcomes the smaller surface area, and the consequentially small particle population of a given quantity, of the usual and typical, random, mechanically mixed, granular corrosion inhibitors commonly employed in practice. The above deficiencies have previously restricted the efficiency and effectiveness of volatile corrosion inhibitors. The restrictions imposed by a comparatively small surface area and a small particle pollution are even further hampered as the surfaces of the corrosion inhibiting granules themselves become progressively inefficient with time and by secondary contamination. A hostile and unfavorable environment usually aggravates the situation and results in a further loss of efficiency and hence effectiveness.
These serious deficiencies are essentially negated by the use of the invention's unique combination of the transport carrier and the transported impregnated component (s). This unique combination maintains the surfaces of the impregnated volatile corrosion inhibitor cleaner and each cavity is under a slight positive pressure and, hence, more readily efficient and effective when placed in hostile environments. The comparatively large capacity of the carrier system and the larger surface area of the volatile corrosion inhibitor distributed throughout the multiple cavities of the reticulated foam effectively blocks and/or markedly restricts contamination from air-borne particles, e.g. (a) solid phase particles such as dirt, dust, etc. (b) liquid phase particles, such as aerosols, related suspended materials, etc., (c) other materials inherent to and/or associated with the above solid or liquid phases, and (d) reasonable quantities of substances splashed, thrown, etc. into the region occupied by or onto the corrosion inhibiting device.
The serious deficiencies mentioned earlier are further negated by the deaeration and the solvent impregnation of the multiple cavities of this unique carrier when followed by the selective evaporation of the solvents. The carrier creates an enormous expansion of the semi-trapped or semi-containerized active component (s), which favors their positive partial pressure(s).
In the case of impregnation of one, two, three or more volatile corrosion inhibitors, the cavity walls are covered and the cavities themselves are partially filled with porous structure exhibiting a very large surface area analogous to that of a natural sponge. Recovered materials show depressed melting points.
2. Description of the Prior Art
The concept of corrosion inhibition in which a mono-molecular layer is deposited on the surface to be protected is well known. Volatile corrosion inhibitors are described in an article by Boris A. Miksic titled "Volatile Corrosion Inhibitors Find A New Home", and published in Chemical Engineering, Sept. 26, 1977. The concept of using a dimensional mass of an ester sponge having a single excavated cavity therein for holding mechanically placed granular random mixed corrosion inhibitors is shown in the Skildum U.S. Pat. No. 3,836,077. Briefly, the Skildum patent shows a device for protecting structures from corrosion, or the like, during storage, where the carrier has at least one such mechanically excavated opening therein. The opening contains a simple mechanically blended, solid, granular mixture of organic ammonium nitrites, fungistats, and anti-oxidants to provide corrosion protection. A further type of corrosion inhibiting invention is shown in the Wachter, et al., U.S. Pat. No. 2,643,176 in which various comparatively solid absorbent materials, derived from natural products, such as, cellulosic substances and their derivatives, including papers, cardboard, fiber-board, wood, cotton cloth and the like are coated, impregnated or otherwise contain one or more of the vapor phase inhibitors The Miksic U.S. Pat. No. 4,051,066 teaches incorporation of a corrosion inhibitor into an elastomer rubber mixture and suggests that it is known that the prior art uses hollowed-out reservoirs (for holding vapor phase inhibitors) and uses recepticles comprised of a porous or open cell material such as foam rubber, Kraft paper, cloth, paperboard, felt or sponge. The Miksic U.S. Pat. No. 4,051,066 further theorizes that all of the prior art material can be impregnated or coated with the inhibitor material. While theorized as possible, the impregnation of ordinary foam rubber materials was not believed to be sufficiently stable, since foam rubber degrades in a corrosive environment; however, it has been discovered that an isocyanate-derived polymer foam provides an excellent, physically and chemically stable carrier, for either single or multiple inclusions of vapor phase inhibitors intended for placement in corrosive and environmentally hostile location, even in inaccessible remote sites, where long life and high stability are essential.
The Jennings U.S. Pat. No. 3,642,998 shows a corrosion inhibiting tool box which is designed to close as tightly as possible. Located in the bottom of the Jennings tool box is an open celled foam material which forms a carrier for a volatile corrosion inhibitor. The volatile corrosion inhibitor comprises granules of volatile amine nitrite which are emitted from the carrier upon placement of a tool on the carrier. Jennings suggests the use of dicyclohexyammonium nitrite and diisopropylammonium nitrite and mixtures thereof with the volatility in the range of 10.sup.-3 to 5.times.10.sup.-2 millimeters of mercury at 68.degree. F. Jennings requires that the box be as tightly closed as possible and that the placement of tools in the tool box causes flexure of the foam to expel vapor therefrom.
The Korpics U.S. Pat. No. 3,803,049 teaches that the mixtures of benzotriazole and tolyitriazole act as a vapor phase corrosion inhibitor for copper and copper alloys without the use of a solvent system.
The Lieber U.S. Pat. No. 2,512,949 teaches the treatment of a fiberous material such as paper textures, etc. with a volatile compound. The fiberous material emits a vapor which deposits a corrosion inhibition film on metal objects. Lieber utilizes amines and amino alcohols as the volatile compound.
The Wachter, et al., U.S. Pat. No. 2,943,908 teaches compositions of vapor phase inhibitors which contain fungicidal properties to inhibit fungus growth during storage of metals. Specifically, Wachter teaches that compounds of dicyclohexylammonium nitrite, dicyclohexylammonium nitrophenate, diisopropylammonium nitrite, cyclohexylammonium nitrophenate can be used.
The Wachter, et al., U.S. Pat. No. 2,752,221 teaches improved vapor phase corrosion inhibitors which are made of a basic acting agent and an organic nitrogen base salt of nitrous acid. The suggested nitrogenous bases are primary amines such as isopropylamine, cyclohexylamine, benzylamine, allylamine, secondary amines, such as diethyl or diisopropylamine, dicyclohexylamined, peperidine, triisopropylamine and higher homologues thereof.